Venetian blinds are well-known window coverings. They have a series of horizontal slats hung from ladders which extend between a top rail and a bottom rail. The slats can be rotated between an open, see through position and a closed position. Additionally, the blinds can be raised and lowered. Venetian blinds contain aluminum, plastic or wood slats and are available in a limited number of colors.
Draperies are another common window covering. Draperies are available in a variety of materials and colors. Commonly a designer will provide a sheer curtain which permits some passage of light in combination with a heavier drapery through which light cannot pass. Consequently, the owner of that drapery system may have a completely open window, a window covered by the sheer which allows for daytime privacy, some passage of light and a view of the outside; or a window covered by the heavier drapery and a sheer which allows night time privacy, little passage of light, and no view of the outside.
Fabric window coverings and draperies are often preferred by consumers over venetian blinds because they have a softer appearance. However, draperies do not have the ability to control the amount of light transmitted through the window covering in a manner similar to louvered blinds like the traditional venetian blind.
Several attempts have been made to provide a fabric window covering with the ability to control the amount of light entering the room. Shapiro in U.S. Pat. No. 3,851,699 discloses a window draw drape having spaced apart light impeding and light transmitting vertical sections. The light impeding sections can be rotated to cover all or portions of the light admitting sections. The light impeding sections are vertical slats attached to the drapery or tightly woven fabric. The light admitting sections are open mesh. This product is difficult to operate because the light impeding sections tend not to align with the light admitting portions when those sections are rotated.
In U.S. Pat. No. 5,313,999 to Colson et al. there is a window covering having first and second parallel sheer fabric sides and a plurality of light impeding or somewhat light impeding vanes extending between the sheer fabric sides. The vanes are angularly controllable by relative movement of the sheer fabric sides. Like the combination of a sheer fabric and a light impeding fabric this system allows the user to have a fully open window, a sheer covered window allowing light transmission with day time privacy and a covering providing night time privacy or room darkening. In addition it has intermediate light control of a louvered product like venetian blinds. The Colson window covering system is difficult to manufacture, has a limited range of fabrics it can use, and has a very flat appearance when in the light impeding mode.
Another light control window covering system is disclosed in U.S. Pat. No. 3,384,519 to Froget. The window covering disclosed there consists of two cloth layers spaced apart by movable parallel blades having each of their marginal edges heat welded to one of the movable cloth layers. With this window covering relative movement of the two cloth layers in a direction perpendicular to the blades changes the angle of the blade and thus controls the amount of light emitted through the article. Because the blades must be heat welded to the cloth layers, only thermoplastic materials can be used. Also, heat welding necessarily requires a melting of some of the fibers of the material bonded, thus providing an uneven outer appearance along the heat welds and producing unwanted crimps or creases of the material which can result in fatigue failure. Furthermore, heat welding is a relatively slow process and the resulting weld is limited in strength.
Judkins in U.S. Pat. No. 5,339,882, discloses a window covering having a series of slats connected between two spaced apart sheets of material. The slats are substantially perpendicular to the sheets of material when the covering is in an open position. The slats are substantially parallel to the first and second sheets of material when the window covering is in a closed position. This product has many of the same limitations of the window covering disclosed by Colson.
There is a need for a window covering system which provides the light control of a venetian blind with the soft appearance of draperies and pleated shades. This window covering should be available in a wide variety of fabric, colors and styles. The system should be easy to install and to operate and able to be manufactured at a cost which allows the product to be sold at a competitive price.